The police did not release the names of the suspects or the universities they attended.

"Right now, for sake of investigation, we can't tell you their identities, but I can confirm that they are Bangladeshi," Ahmed said.

The operation came a month after gunmen stormed a restaurant and bakery in an upmarket area of the capital and killed 22 people after a hostage siege, including nine Italians, seven Japanese, an American and an Indian.

The Islamic State of Iraq and the Levant group (ISIL) later claimed responsibility for the attack.

Many Bangladeshis were shocked to discover that three of the five attackers, who were all killed in an army raid that ended the siege, had attended some of the country’s most prestigious private schools.

The men had gone missing from their homes in the months before the attack.

On Monday, authorities released a list of 68 names of young people whose families had reported them missing, suggesting some of them could have joined armed groups.